Derivative Position of Company (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Derivative Financial Instruments, Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	$ 2,176		$ 1,913
Netting	(354)	[1]	(294)	[1]
Total	1,822		1,619
Derivative Financial Instruments, Liabilities
Derivatives, Fair Value [Line Items]
Fair Value, Liabilities	2,640		2,554
Netting	(1,687)	[1]	(1,889)	[1]
Derivative Liabilities	$ 953		$ 665

[1] Represents netting of derivative asset and liability balances, and related collateral, with the same counterparty subject to master netting agreements. At September 30, 2012, the amount of cash and money market investments collateral posted by counterparties that was netted against derivative assets was $89 million and the amount of cash collateral posted by the Company that was netted against derivative liabilities was $1.4 billion, compared with $88 million and $1.7 billion, respectively, at December 31, 2011.